Stoichiometry

# Stoichiometry

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## Stoichiometry

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##### Presentation Transcript

1. Stoichiometry What’s that you said?

2. What is Stoichiometry? • Stoichiometry is the numerical relationships in chemical reactions.

3. Let’s build a Tricycle(aka FSW3HP2) • For each tricycle we need : • 1 frame (F) • 1 seat (S) • 3 wheels (W) • 1 handlebar (H) • 2 pedals (P) • The “chemical equation” for building a tricycle would look like: F + S + 3W + H + 2P → FSW3HP2

4. Tiny Tyke Workshop • The Tiny Tyke workshop is scheduled to make 640 tricycles. How many wheels should be in the workshop to make these tricycles? • Analyze the knowns and unknowns: • Known: • The # of tricycles we need to build = 640 tricycles • Bal eq: F + S + 3W + H + 2P → FSW3HP2 • This balanced equation represents the formation of a single tricycle (FSW3HP2) • Therefore TT needs to make 640 FSW3HP2

5. Unknown: • number of wheels = ? Wheels 3 W 1 FSW3HP2

6. We now solve for the unknown: 640 FSW3HP2 3 W = 1920 W 1 FSW3HP2 So you need 1920 wheels to make 640 tricycles. • Does this make sense??

7. Tiny Tyke has decided to make 288 tricycles each day. How many seats, wheels and pedals are needed? • Do this as 3 separate problems: • Set up your ratios first: 1 S 3 W 2P 1 T 1 T 1 T • Now plug in what you’re given: 288 trikes 1 seat = 288 seats 1T

8. 288 trikes 3 W = 864 wheels 1 T 288 trikes 2 P = 576 pedals 1 T

9. Stoichiometry • Based on chemical equations and the law of conservation of matter • Must know the balanced chemical equation for the reaction we are studying first • You can determine the quantities of reactants and products in a chemical reaction from reaction stoichiometry

10. There are 4 types of reaction stoichiometry problems: • mole-mole problems: • moles of A → moles of B • mole-mass problems: • moles of A → moles of B → mass of B • mass –mole problems: • mass of A → moles of A → moles of B • mass-mass problems: • mass of A → moles of A → moles of B → mass of B • What step do they all have in common?

11. Mole ratio • The relationship between the number of moles of reactants and/or products in a chemical equation. • N2 (g) + 3 H2 (g) → 2NH3 (g) • The mole ratio of H to N is 3 : 1 • So… for every 1 mole of nitrogen, I need 3 moles of hydrogen • (and will produce 2 moles of ammonia)

12. Now lets Pracitce • In the Synthesis of water, if I start out with 42 grams of H2 and an excess of 02, how much water will I have at the conclusion of the reaction?

13. Write the equation H2 + O2  H2O • Balance the equation 2H2 + O2  2H2O • Start with what you know • 42 g H2